The invention relates to a method for switching transmission devices to an equivalent circuit for bidirectional transmission of ATM cells.
Such a method is already known from the international patent application WO94/28646.
This known method relates to transmission devices of the synchronous digital hierarchy (SDH). Here, a transmission device for the bidirectional transmission of digital signals is provided, in which device two switching centers which function as terminals are connected to one another via a service link and a standby link. The two terminals each contain a monitoring device for detecting transmission faults. A switching device which can be controlled by the monitoring device connects a reception device into a first switched state with the service link and in a second switched state with the standby link. Control information is exchanged between the control devices of the two terminals. The switching devices are each controlled by the local monitoring device as a function of local control criteria which are contained in the control information received from the opposite station.
It is a disadvantage here that this known method relates to transmission devices of the synchronous digital hierarchy and cannot be transmitted on transmission devices of the asynchronous transfer mode (ATM). Furthermore, this known method is used on 1+1 and 1:1 structures. However, in relatively complex structures such as 1:n structures, for example, incorrect connections may occur.
In addition, the publication IEICE Transactions on Communications, Vol. E78-B, No. 7, Jul. 1, 1995, pages 987-994, Mitsuhiro Azuma et al. (XP532482) discloses a method and a device for switching ATM links to an equivalent circuit. If a node or a link fails, a standby link is switched to. 1:1, 1+1 or 1:N structures are, however, not referred to here.
The invention is based on the object of developing a method of the type mentioned at the beginning in such a way that cells which are transmitted according to an asynchronous transfer mode can be transmitted via a plurality of network nodes with a high degree of reliability.
An advantage of the invention is, in particular, that just one standby link is provided and it is assigned to a plurality of service links. The ATM cells of the faulty service link are transmitted on this standby link in accordance with priorities. The receiving switching center then performs switching through operations using a logic operation number. This provides the advantage that in the case of a fault the advantage can be maintained without restriction.
In general terms the present invention is a method for switching transmission devices to an equivalent circuit for the bidirectional transmission of ATM cells. Two switching centers terminate a transmission section formed from a plurality of service links and feed. the information in ATM cells to a respective receiving switching center on the plurality of service links. Monitoring devices are each arranged at the end of a service link and determine a fault on the service link. One standby link is provided between the two switching centers. In the case of a fault on one of the service links, the ATM cells, which are transmitted on the service links, are transmitted on the standby link in accordance with priority criteria and logic operation information contained in the cell header of the ATM cells and are fed to further devices of the ATM network. A priority is assigned tot he service links and to the standby link.
Advantageous developments of the present invention are as follows.
In the event of switching to an equivalent circuit, an equivalent circuit request, to which further priorities are assigned, is generated.
The logic operation information is the number of the virtual path.
Priority tables, in which the priorities are defined, are provided.
The switching to an equivalent circuit is carried out by driving a switching device contained in the transmitting switching center and by using a selection device arranged in the receiving switching center.
The selection device is embodied as an ATM switching matrix.
Special data is transmitted on the standby link during times which are free of service faults.
When an equivalent circuit request arrives in the receiving switching center, an equivalent circuit switching protocol is generated, which is fed just once to the remaining switching center on the standby link.
Total failure and degradation of a service link are determined in the monitoring device of the receiving switching center.
Switching device can be set permanently.
The switching centers are embodied as cross connect switching devices.